ELECTROCHEMICALLY TUNABLE TWO-DIMENSIONAL MEMBRANES FOR IONIC AND MOLECULAR SIEVING

Abstract

Purifying mixtures is still a tough objection currently. Conventional separation processes based on thermal or chemical methods would higher global energy consumption and pollution emission. Hence, alternative routes need to be explored to separate chemicals more efficiently and eco-friendly. Membranes with preeminent perm-selectivity are essential for processes such as water purification and desalination, pharmaceutical manufacturing, resource mining, etc. Although traditional polymer membranes already showed substitutability in these fields, most of them were restricted by materials’ trade-off effect, that is, high permeability and selectivity couldn’t be achieved at the same time. In the past decade, nanolaminate membranes made of restacked two-dimensional (2D) materials such as reduced graphene oxide (rGO) are demonstrated to be promising candidates for ionic and molecular sieving via size-limited diffusion through the interlayer gaps. However, the biggest challenge is that the interlayer spacing is hard to control and manipulate continuously and reversibly, leading to limited and poor performance in separating ions or molecules of similar sizes. This project proposes a new concept of electrochemically tunable membranes by introducing redox-active molecular spacers between rGO nanolaminates via π-π interaction. Redox agents such as ferrocene and its derivatives are sensitive to electrochemical potential stimuli, which can lead to changes in charge density and hydration level of the interlayer environment to achieve precise tuning in interlayer spacing. This tunable membrane is a promising candidate for next-generation separations that can not only adapt to the demands of various scenarios in the chemical and pharmaceutical industries but also play a pivotal role in energy generation like reverse electrodialysis.